About half of people over the age of 50 have been screened for colorectal cancer, according to a new survey, but health officials say that number is still far below what it should be.

"Colorectal cancer is one of the leading cancer killers in the United States, behind only lung cancer. Screening has been shown to significantly reduce mortality from colorectal cancer, but a lot of people are still not getting screened," said Jean A. Shapiro of the Centers for Disease Control and Prevention.

Shapiro said that 24.1 percent of people without health insurance had the test, a rate far below the general population.

"If we can increase the number of people who have health care coverage, we should be able to increase colorectal cancer screening rates," said Shapiro.

The screening rate in 2000 was about 43 percent.

Shapiro said the increase may have been due in part to increased media coverage. However, in 2001, Medicare also expanded its coverage for colonoscopy screenings to a wider range of patients.

People who were college educated and those who had higher incomes were also more likely to get a colonoscopy.